CVE-2021-21978: VMware View Planner RCE Vulnerability

CVE-2021-21978 Overview

CVE-2021-21978 is a critical remote code execution vulnerability affecting VMware View Planner 4.x prior to version 4.6 Security Patch 1. The vulnerability stems from improper input validation and lack of authorization in the logupload web application, allowing unauthorized attackers with network access to upload and execute specially crafted files within the logupload container.

Critical Impact

An unauthenticated remote attacker can achieve arbitrary code execution on VMware View Planner systems by exploiting the file upload vulnerability in the logupload web application, potentially leading to complete system compromise.

Affected Products

• VMware View Planner 4.x versions prior to 4.6 Security Patch 1
• VMware View Planner 4.6 without Security Patch 1

Discovery Timeline

• 2021-03-03 - CVE-2021-21978 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-21978

Vulnerability Analysis

This remote code execution vulnerability exists in the logupload web application component of VMware View Planner. The application fails to properly validate user-supplied input and lacks adequate authorization controls, creating conditions where an attacker can upload arbitrary files to the server. Once uploaded, these malicious files can be executed within the context of the logupload container, granting the attacker code execution capabilities on the target system.

The vulnerability is particularly severe because it requires no authentication and can be exploited remotely over the network. The logupload functionality, intended for legitimate log collection purposes, becomes an attack vector when it accepts and processes files without verifying the identity of the requester or the nature of the uploaded content.

Root Cause

The root cause of CVE-2021-21978 is improper input validation (CWE-20) combined with missing authorization checks in the logupload web application. The application accepts file uploads without:

1. Verifying the authenticity or authorization of the requesting party
2. Validating the type, content, or structure of uploaded files
3. Restricting the upload path or execution permissions of uploaded content

This combination of weaknesses allows attackers to bypass security controls entirely and upload executable payloads.

Attack Vector

The attack is network-based and requires no user interaction or prior authentication. An attacker with network access to the VMware View Planner Harness can directly target the logupload web application endpoint. The exploitation flow involves:

1. Identifying a vulnerable VMware View Planner instance accessible over the network
2. Crafting a malicious payload designed to execute within the logupload container environment
3. Submitting the payload to the logupload web application endpoint
4. Triggering execution of the uploaded file to achieve remote code execution

The vulnerability mechanism involves exploiting the file upload functionality in the logupload web application. Due to insufficient input validation and missing authorization controls, the application accepts arbitrary file uploads from unauthenticated sources. Attackers can leverage this to upload web shells or other executable content that runs within the container context. Technical exploitation details are available in the Packet Storm RCE Exploit.

Detection Methods for CVE-2021-21978

Indicators of Compromise

• Unexpected files appearing in the logupload web application directories
• Unusual outbound network connections originating from the VMware View Planner container
• Anomalous HTTP POST requests to logupload endpoints containing non-standard file types
• Evidence of web shell presence or unauthorized scripts within the application environment

Detection Strategies

• Monitor HTTP traffic to VMware View Planner for suspicious POST requests targeting the logupload functionality
• Implement file integrity monitoring on VMware View Planner installation directories to detect unauthorized file creation
• Deploy network-based intrusion detection signatures targeting exploitation patterns for this vulnerability
• Review web server access logs for unusual request patterns or unauthorized upload attempts

Monitoring Recommendations

• Enable comprehensive logging for the VMware View Planner logupload web application
• Configure SIEM alerts for anomalous file upload activity or unexpected process execution within the View Planner container
• Establish baseline behavior profiles for View Planner network communications to identify deviations
• Implement egress filtering and monitoring to detect potential post-exploitation command and control traffic

How to Mitigate CVE-2021-21978

Immediate Actions Required

• Apply VMware View Planner 4.6 Security Patch 1 immediately to all affected installations
• Restrict network access to VMware View Planner Harness to authorized administrative networks only
• Audit existing View Planner deployments for indicators of compromise before and after patching
• Consider temporarily disabling or isolating vulnerable View Planner instances if immediate patching is not possible

Patch Information

VMware has released Security Patch 1 for View Planner 4.6 to address this vulnerability. The patch is available through the official VMware download channels. Administrators should consult the VMware Security Advisory VMSA-2021-0003 for detailed patching instructions and additional guidance.

Workarounds

• Implement network segmentation to restrict access to VMware View Planner instances from untrusted networks
• Deploy web application firewall (WAF) rules to filter malicious upload requests targeting the logupload endpoint
• Use firewall rules to limit access to the View Planner Harness to only necessary administrative IP addresses
• Enable enhanced logging and monitoring until patches can be applied

# Example: Restrict network access to VMware View Planner using iptables
# Allow only trusted administrative network (example: 10.0.1.0/24)
iptables -A INPUT -p tcp --dport 443 -s 10.0.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP